Numerous types of pivotable wall beds, desks, tables and other pieces of furniture are known in the prior art and are widely used in situations in which available space is at a premium. The bed or other piece of furniture is provided with hinges so that it can be pivoted upwards from its generally horizontal-use position to a generally vertical storage position adjacent a wall or in a small closet placed in a wall for that purpose.
Since the weight of even a medium-sized wall bed can be considerable, counterbalance springs have long been used to make it easier for a person to move the bed between the in-use and storage positions. The same situation exists with respect to all types of pivoting loads, including, but not limited to, fold-up desks, tables, work counters, loading ramps or doors hinged at the bottom, or any member pivoted near the bottom for movement between a generally vertical to a generally horizontal position. For purposes of illustration, the invention disclosed herein is applied to a pivotable wall-type bed, but it will be understood that the present invention is equally applicable to any of the pivoting type loads discussed above.
While a counterbalance mechanism can greatly reduce the amount of force needed to move a rotatable wall-type bed between its use and storage positions, the application of a small force can still be burdensome to some persons. The invention disclosed in U.S. patent application Ser. No. 99,655 to K. Wilson and R. Bue, the disclosure of which is incorporated herein, is directed to a power operated rotatable support structure. A motor means is shown assisting a counterbalance means in providing the force required to move a support structure between its horizontal and vertical dispositions. The motor means is comprised of an electric drive motor which drives a reciprocal drive arm in a generally linear direction. The drive arm is coupled through at least one linkage arm to the support member. The linkage arm is pivotable at its point of connection to the drive arm and also at its point of connection to the support member. In order to transfer the linear motion of the drive arm to pivoting motion of the support member, a means for yieldably holding a linkage arm relative to the support member is provided. Several embodiments of the holding means are shown. None of the holding means disclosures in this patent application provides for both a yieldable connection between the drive arm and the support member combined with an automatic disengagement of the rotational linkage between the drive arm and the support member with subsequent automatic reengagement. Thus, the various prior art systems provide for either a manually operated rotatable bed having a counterbalance means or for a power assisted rotatable bed having a motor means in addition to a counterbalance means. The prior art, however, does not show any mechanism which can provide both features.